The renal outer medullary potassium (ROMK, Kir1.1) channel is a weak inward rectifying K+ channel with a key role in renal K+ recycling and secretion (Ho et al., Nature, 1993, 362, 31-38; Shuck et al., The Journal of Biological Chemistry, 1994, 269(39), 24261-24270; Lee and Hebert, American Journal of Physiology-Renal Physiology, 1995, 268(6), F1124-F1131; Lu et al., The Journal of Biological Chemistry, 2002, 277, 37881-37887; and Hebert et al., Physiological Reviews, 2005, 85:319-371). In the thick ascending limb (TAL) of a nephron, ROMK channel activity provides the K+ gradient necessary for Na and Cl reabsorption by the Na+—K+-2Cl− (NKCC2) co-transporter. In the distal convoluted tubule (DCT) and cortical collecting duct (CCD), ROMK channels form the major secretory pathway for K+ and as a result, play an important role in K+ homeostasis under physiological conditions (Welling and Ho, American Journal of Physiology-Renal Physiology, 2009, 297(4): F849-F863).
Multiple lines of evidence indicate that inhibition of ROMK channel activity results in natriuresis, diuresis and reduced blood pressure. Therefore, ROMK inhibition may offer a novel mechanism of blood pressure regulation and diuresis in patients suffering from hypertension, congestive heart failure or any other edematous disease conditions. The activity of NKCC2 transporter is tightly coupled with ROMK activity in the TAL region and homozygous loss of function mutations in ROMK in humans result in a disease phenotype (renal salt wasting, increased aldosterone levels, metabolic alkalosis, reduction in blood pressure) very similar to that of NKCC2 homozygous mutations but with a milder hypokalemia (Simon et al., Nature Genetics, 1996, 14: 152-156). In addition, humans identified with heterozygous ROMK mutations from the Framingham Heart Study presented with reduced blood pressure (Ji et al., Nature Genetics, 2008, 40(5): 592-599). Similar to human genetics, mouse genetics also support the role of ROMK in Na+ reabsorption in the kidney and overall blood pressure regulation (Lu et al., The Journal of Biological Chemistry, 2002, 277, 37881-37887; and Lorenz et al., The Journal of Biological Chemistry, 2002, 277: 37871-37880). Furthermore, pharmacological blockade of the ROMK channel has been shown to induce natriuresis and diuresis in rats upon acute dosing and in dogs upon both acute and prolonged dosing (Tang et al., Bioorganic and Medicinal Chemistry Letter, 2013, 23: 5829-5832; Garcia et al., The Journal of Pharmacology and Experimental Therapeutics, 2014, 348: 153-164; Walsh et al., ACS Medicinal Chemistry Letters, 2015, 6: 747-752; and Dajee et al., Circulation, 2014, 130: A12397). Since the ROMK channel is also implicated in regulation of net K+ secretion in the distal part of the nephron, it is believed that ROMK inhibition in this region will mitigate the K+ wasting and hypokalemia associated with loop and thiazide diuretics. Acute or prolonged (up to 122 days) ROMK antagonism does not lead to kaliuresis or hypokalemia in dogs (Garcia et al., The Journal of Pharmacology and Experimental Therapeutics, 2014, 348: 153-164; Walsh et al., ACS Medicinal Chemistry Letters, 2015, 6: 747-752; Dajee et al., Circulation, 2014, 130: A12397). Together, these data suggest that inhibition of ROMK may produce diuretic efficacy that is equivalent to or better than currently available loop diuretics and with potentially lower incidence of hypokalemia.
WO 2015/095097 discloses compounds useful as inhibitors of ROMK. Other publications disclosing compounds useful as inhibitors of ROMK include WO 2010/129379, WO 2010/136144, WO 2012/058116, WO 2012/058134, WO 2013/028474, WO 2013/039802, WO 2013/062892, WO 2013/062900, WO 2013/066714, WO 2013/066717, WO 2013/066718, WO 2013/090271, WO 2014/015495, WO 2014/018764, WO 2014/085210, WO 2014/099633, WO 2014/126944, WO 2014/150132, WO 2015/017305, WO 2015/065866, WO 2015/095097, WO 2015/100147, WO 2015/105736, WO 2016/008064, WO 2016/010801, WO 2016/010802, WO2016/060941, WO2016/065582, WO2016/065602, WO2016/065603, WO2016/069426, WO2016/069427, WO2016/069428, WO2016/069430, WO2016/091042, WO2016/122994, WO2016/127358, WO2016/130444, CN105693706, and WO2016/091042.
In view of the numerous conditions that are contemplated to benefit by treatment involving inhibition of ROMK, it is immediately apparent that new compounds capable of inhibiting ROMK and methods of using these compounds should provide substantial therapeutic benefits to a wide variety of patients.
The present invention relates to a new class of compounds found to be effective inhibitors of ROMK.